[5117]

That video showed the bike & 911 riding together on the Nurburgring...



No way the rider can hang it all out when he's got a 3500+ lb car on the track with him, as well as all the minivans, etc.. that they pass during the video.



There are various articles in car magazines from time to time poppping up to prove that someone's $100,000 penis attachment is faster than a bike. Usually there is some car guy riding the bike.



The most interesting one was Kevin Schwantz riding the Gixxer 1000 and Z06 back to back last year in Motorcyclist. Schwantz has raced pro in both car & motorcycling racing. He turned in a time close to the SCCA record in the Corvette... he was so much faster on the Gixxer that they said he would be lapping the corvette every 10 laps. He was actually going way faster through the corners on the bike too, not just on the straights.



Basically if the rider is very good no car is going to beat an expert racer on a track unless it is an open wheel race car. (1500lbs, 600-900hp, lots of downforce) Open wheel race cars (CART, IRL, F1, etc..) will demolish a Superbike or GP bike. There will never be a street car with that kind of performance, as the downforce will cause it to get about 5mpg. Who knows at what point the cars are faster.. but it is nowhere near a street car. Maybe a Le Mans Prototype class car is faster? Maybe a GTS?



Think of it this way.. the car has four big tires. But they aren't THAT much bigger than the bike tires. At full cornering the car is transferring most of it's weight onto the two outside tires.



But most of all the important thing is the car + driver weigh 8-10x as much as the bike and rider do. There is no way to get around physics. The only way for the car to corner better than the bike is by having massive downforce. Many high end cars have neutral aerodynamic forces, but very few have significant downforce due to the drag it creates.



Ben

 

[bdesmo]

Couldn't agree more here in the UK we have the Touring car championship which is supposed to emulate prodie cars. They run on the same tracks as the British Superbikes. For example at Knockhill in Scotland the top cars were lapping at best in the mid 54s while John Reynolds qualified in a 50.7, nuff said.

 

[Andonyx]

I have some background in physics, although it's wave physics, but most of the parameters brought up here are pretty basic...



First let's clear up a mis-conception about how friction works. Friction is a coefficient, which means when we have fixed mesaurement such as how many pounds of force are pressing two surfaces together, then we can use the coefficient of friction of the surfaces, which for most regular surfaces can readily be looked up in a table, to determine how much friction exists between the surfaces.



But something that does NOT effect that final measure is surface area.



See surface area is great for traction in a non-perfect world where at any given time parts of the road or tire might have slick spots, grease, or imperfections which will allow for momentary loss of contact with the road. More surface area means more reassurance that the friction you should have by mass of the vehicle and types of surfaces is maintained even over imperfections and temporary unfavorable circumstances. But more tires does NOT equal more friction.



Think of it this way. If you have a 600 Pound bike and four square inches of contact patch you have rubber pressing against ground at about 150 LBS / square inch, over four inches.



If you only had one square inch of contact patch that seems really bad, except that now that one square inch is pressed to the road at 600LBS / square inch. Which sliding over a surface, or rolling over a surface has the same total friction as the four square inches expressed as a coefficient.



The disadvantage is that if you go over a one square inch pothole, you can lose ANY friction you have for that instant, which in a tight turn could be enough to screw you.



Now I haven't seen the video either, so I don't know what happens, but If the Porsche which let's admit is a really well engineered car, beat the bike in the turns I would guess it has to do with where energy is absorbed when turning.



In a perfect world, one uses energy whenever they are accelerating. And acceleration is defined as change in velocity. Velocity inlcudes both a speed and a direction component, so acceleration can be changing either one of those measurements. So, if you are turning, and you aim to cover exactly the same amount of ground per second as when you were going straight, you need to put a little more energy into changing the direction of the car. Which is why you'll notice in a long enough sweeper, if you want to maintain the velocity you had entering the turn you have to give it just a tad more throttle.



Much of that energy is dissapated through friction on the tires. Tires only have a finite amount of friction. In a straightaway, you can use all of this friction to accelerate the car forward, in a turn some of that friction must be used to change the heading of the car. (Remember in a no gravity situation in space, something moving tends to stay moving forever in a straight line. But you need to apply force to change it's direction.) If you exceed the total amount of friction by turning to hard, or accelerating too hard through a turn, you break the wheels loose.



Now I don't think Bikes have inherently any more problems staying tacked to the road based on tire material, road surface (Obviously in this test it was the same) or even mass distribution. If I had to guess, I'd say it has to do with the mechanics of how a bike turns.



When you alter course from a straight line in a moving mass, you are fighting the inertia of the mass. This is most easily demonstrated in the illusion of centrifugal force. In reality, there is no force that says things moving in a circle want to move to the outside of the circle. It's just that an any given time, if the force "tethering" the object to the circular path were removed, the object would continue to move in a straight line.



In a bike you not only fight this by turning, you fight this by leaning the bike in. It takes energy to alter the heading of the bike, and additional tire friction is used to hold the bike in it's leaned over position when obvisouly, without that effort the top of the bike would stand up, and probably roll to the outside of the turn. (Assuming that standing it up didn't settled it back into a straight line immediately.) In the case the tires serve as the fulcrum of a lever, and when you push the bike over to one side what keeps the bike form rotating about it's Z axis is the friction of the tires on the road, which you are borrowing from to do that.





The car on the other hand has its axis in between the tires, and as you throw it into the turn, the body rolls to the outside of the turn actually counterbalancing some of the force the tires have to absorb to change the cars direction, and mitigating some of the "centrifugal" effect. Finally as it does so, while the tires on the inside lose some force to the ground, the tires on the outside gain some making for a zero-sum type proposition. But nither set of tires is used as the pivot point for that body motion on the Z axis and so nothing additional is subtracted form the friction they use to both keep the car moving forward, and to change it's velocity.



Anyway that's all just a guess.

 

[kpaul]

Excellent, let see what sportbike_pilot says as well

Excellent points about the following:

Friction, Acceleration, leaning the bike(tires as a fulcrum), and the cars axis. I have a degree in Electrical Engineering so my Dynamics knowledge is limited to Fundamental classes in Physics and ME Dynamics and of course my memory. I started drawing a free body diagram of the bike vs car. Sportbike_pilot is the college Physics Instructor he should be able to tie up any loose ends. Good effort to explain.

 

[kpaul]

Excellent

Yep I remember that article abot the Schwantz as well. Yep Open wheel race cars are incredible.

 

[4940]

Re: Excellent, let see what sportbike_pilot says as well

I don't have a degree in physics, but I did stay at a Holiday Inn last night. Somebody please administer the euthanasia before it's too late. VWW

 

[kpaul]

Re: Excellent, let see what sportbike_pilot says as well

Now that's funny. Good one.

 

[25850]

INFO OVERLOAD ALERT ...

my brain hurts. allow me to summarize:

cars suck.

bikes rock.

engineers ... can't live with 'em, can't live without 'em.

sheesh.

 

[23063]

I thought it was pretty well known that a race car can corner faster than a bike. The car has four wheels and a lot more traction for its low center of gravity.



On the street, passenger cars have to corner through a narrow lane and they are built with soft suspension for comfort so the car rolls back and forth through corners, whereas a bike can take a very different line through a corner and leans into the corner so suspension can operate in a vertical plane. But, mostly I think bike riders ride better than car drivers drive.



Have you ever been up in the mountains and encountered a car flying through the corners? There are a few guys out there that can really corner hard.

 

[dp5]

i've run both cars and bikes on a track extensively. i'm a decent driver and an ok rider, though not a pro by any stretch. all in all i've run about 3,000 laps at portland in a variety of machinery (see www.dpcars.net for details and tons of video, if you care). i've generally been faster in cars. this is not because cars are faster, they are just easier and more comfortable to push the limits in. the skill of the operator matters a lot in both cases (i pass corvettes and 911s in my stock, street-tired mini all the time), but on a bike it's just much more so. while in cars i might be only a second off the pace that a top club racer could post in the same machine, on a bike i'm more like 6-8 seconds off. my best effort on the R1 i recently got is a 1:20 flat (hoping to get below that next track day), a decent amateur racer time on the same bike and tires would be in the 1:14 range.

bottom line is, unless you have experienced and skilled drivers/riders at the controls any such 'contests' are completely meaningless. earlier this year i rented a 1.6L golf and ran it on the nurburgring in germany. i was able to keep up with a 911-C4 and passed a bunch of bmws, porsches and a maserati in the process. that doesn't mean that a cheapo rentagolf is faster than those cars!

 

[kpaul]

Nothing beats a bike for fun

I agree bikes are so much more fun. I working on my private pilots license (very slowly) and I have a had sports cars (RX-7, AWD Eclipse, and old Z). Nothing beats a bike. Small planes are 95% boredom, 5% interesting. Cars about the same

"engineers ... can't live with 'em, can't live without 'em." My wifes words exactly.

 

[Abe_Froman]

I happened to download the video you're talking about just last night. It is a first-generation R1 against a 996 Carrera 4s. I forget the name of the track but it is not the 'ring, at least not the public part, and it sure doesn't look like the F1 track either.



The car is driven by an SCCA-type race driver, and the bike is ridden by some Euro superbike rider, pro, supposedly.



The guy on the bike is clearly taking it easy in the turns. I don't recall seeing his knee down at all. The car guy is clearly giving it all he's got. Given that they are both on the track racing each other at the same time, the bike guy is probably understandably cautious lest he go down and get run over by the car.



A much more appropriate comparison would simply judge laptimes as the Schwanz article did in which he thoroughly spanked his car times when riding the bike (though who knows, maybe he was just making sure the bike won, as in this video, where they apparently told the guy to ride slow enough that the car won.)

 

[Abe_Froman]

P.S.-----

Link to the video in question-----

http://www.mnsbr.com/vids/Porsche_Carrera_4_vs_Yamaha_R1.wmv

 

[Abe_Froman]

I was taught that while 'centrifugal' force is a fallacy, 'centripital' force is the proper and legitimate idea, i.e., the force on an object that makes it accelerate constantly (inward around a point in order to make a circle.) In the case of the centerfuge it is the force of the arm pulling the object in towards the center of the circle. Is that not correct?

 

[Dave305]

"I thought it was pretty well known that a race car can corner faster than a bike."



What "race car"? See the posts above. Without significant aero aids for producing downforce on a car, the bike will be faster (given equally skilled operators). Open-wheeled race cars such as F1 can produce HUGE downforce and therefore can corner and accelerate more quickly. Producing significant downforce on a bike is not pratical.

 

[Woody650]

"The guy on the bike is clearly taking it easy in the turns. I don't recall seeing his knee down at all. The car guy is clearly giving it all he's got. Given that they are both on the track racing each other at the same time, the bike guy is probably understandably cautious lest he go down and get run over by the car."



I had exactly the same thought. That rider isn't riding nearly as close to the edge as the driver is, and clearly had to be careful not to get squashed by a car on the track at the same time. Not exactly a fair fight (the rider has far more at risk than the driver) yet the bike only lost by less than a car length.



Comparing lap times between that car and bike on the track at separate times, the bike would have smoked the car.

 

[kpaul]

Having just watched this video, I have to say the bike guy was understandably a wuss. I would not want to race a car on the same track at the same time. As Abe suggested, the only way to do it right would be have seperate runs and compare times. It looks like the bike rider wasn't as agressive probably cause he didn't want to get injured by the porche hitting him. The porche driver was agressive in cutting the bike off on the first and second pass. . By the way the narrator is a prick. Car guys I hate em </a>

 

[kpaul]

And car guys was pretty agressive on those passes.

 

[kpaul]

By the way I use be a Car guy.

 

[Andonyx]

Yup that's pretty much it. In the case of a vehicle, there is not object at the center of the circle pulling you in, it's a case of your turned tires are constantly applying a force trying to accelerate you in a new direction.